Lenses formed from thermoplastic material have enjoyed increasing popularity. Advances in the production of such lenses have included the use of materials that are lighter and free of unwanted color.
An attractive and important way to optimize a plastic lens is by use of materials having a high index of refraction. This enables lens designers to design thinner lenses having surfaces with larger radii of curvature.
Aromatic thermoplastics have been recognized as potential candidates for the fabrication of high refractive index materials for optical applications, particularly in the area of spectacle wear. Aromatic polycarbonates typify this approach to optical applications, and have an index of refraction of about 1.59. These materials are however known to be subject to undersirable chromatic aberration.
Aromatic polyethers that contain the triphenyl phosphine oxide moiety in the repeat unit have been described in the literature. Aromatic polyethers containing the phosphine oxide group are shown or suggested and described in U.S. Pat. Nos. 4,108,837 and 4,175,175. Some work has been attempted on the use of these materials as short range optical fibers, and as plasma-resistant coatings.
These materials may be synthesized by the reaction of a variety of bisphenols with 4,4'-bis(fluorophenyl) phenyl phosphine oxide (BFPPO) in the presence of a base such as potassium carbonate in dipolar aprotic solvents such as N-methyl pyrrollidinone (NMP) or N,N-dimethyl acetamide (DMAC). Techniques for the synthesis of these compounds are known and many of their physical properties are well documented in the literature. See, for example, C. D., Smith, et al, SAMPE Symps Exib. Vol. 35, No. 1, pp 108-22 (1990); R. L. Holzberlein, et al, Polymer Prepr., Vol. 30, No. 1 p. 293 (1989); D. B. Priddy, et al, Polymer Prepr., Vol. 34, No. 1, pp. 310-11 (1993); D. B. Priddy et al, Polymer Prepr. Vol. 33, No. 2, pp. 231-32 (1992); C. D. Smith, et al., Polymer Prepr., Vol. 32, No. 1, pp. 93-5 (1991); C. D. Smith, et al, High Perform. Polymers, Vol. 3, No. 4, pp. 211-29 (1991). Controlled molecular weight with non-reactive end-groups may be generated, for example, by employing a monofunctional monomer such as 4,tert-butyl phenol.